In the method for obtaining an image by an electrophotographic printing method or an electrostatic printing method, an electrostatic image formed on a photoreceptor is developed with toner charged by friction in advance and then fixed.
As the fixing technique, there are a heat roller technique in which the toner image obtained by development is fixed using a pressurized and heated roller and a non-contact fixing technique in which the toner image obtained by development is fixed using an electric oven or flash beam light.
In order to pass through these processes without any problem, toner is required to be able to maintain a stable charged amount and to exhibit favorable fixing property on the paper.
Moreover, toner is also required to be equipped with improved toner characteristics such as storage stability, low-temperature fixing property and hot offset resistance due to the tendency of an increase in speed, miniaturization, energy saving and the like of printers in recent years.
The binder resin for toner is a material that greatly affects the toner characteristics described above. Hitherto, a polyester resin, which is excellent in toughness and fixing property at a low temperature and exhibits a favorable performance balance, has been used as a binder resin.
In addition, the switchover from plastics derived from petroleum raw materials of the related art to biomass-based plastics has been attempted in recent years from the viewpoint of reducing the environmental impact such as global warming suppression.
For toner as well, those which are produced using biomass-based raw materials are desired, and also for the binder resin constituting the toner, those which are produced using biomass-based raw materials are desired.
As the polyester resin produced using a biomass-based raw material, for example, a polyester resin for toner produced using isosorbide derived from a plant raw material as a polyhydric alcohol is disclosed in Patent Document 1.
In addition, a polyester resin for toner produced using isosorbide derived from a plant is described in Patent Document 2.